Earlier quoted context omitted.
There are alcoholic beers that taste as bad or worse as the non-alcoholic ones. And there are alcoholic drinks that taste like they have no alcohol in them at all. Or drinks where you cannot tell if they have any alcohol in them. There are ways to make these things blinded.
> Or drinks where you cannot tell if they have any alcohol in them. Proving this for a sample is pretty much impossible because you’re simply masking it and the sensory performance of humans is highly variable. You can get some imperfect approximation of blinding but it will be a compromise.
If they can still somehow taste the difference between them, then you change your mix so that they can't tell the difference or eliminate them from the study.
This may have other effects on the study, but at least you can be reasonably sure that no one can tell the difference between the substances being tested, except possibly by the effects they feel after consuming the substances in question.